1. Field of the Invention
This invention relates to a card reader and more particularly to an improved firing circuit for electrically energizing oppositely disposed terminals of a card reader.
2. Prior Art
In U.S. Pat. No. 3,562,496 to Fisher a data sensing device utilizing an improved card reader is disclosed. The card reader is adapted to scan a card by sensing the presence of passages extending throug the card. The reader has oppositely disposed electrical terminals separated by a gap into which the card is inserted. The terminals are energized by applying a voltage across the gap so that when the terminals are aligned with the passages a spark traverse the gap. This procedure enables the card reader to sense the pattern of passageways in the card.
Energy is selectively transmitted to the terminals under the control of a silicon control rectifier (SCR) switch. The silicon controlled rectifier causes a charged capacitor to discharge through a transformer and generate a rather large voltage to be applied to the terminals. If electrical energy is transmitted through the passages, that condition is sensed and indicating circuitry signals that a match exists between the passageways and the terminals.
A firing circuit coupled to the silicon controlled rectifier activitates the circuitry by supplying energy to fire the silicon control rectifier and to energize the terminals. The SCR firing circuit disclosed in the '496 patent has been used with success and functions quite well in initiating a scan by the card reader.